modelling of deformable polymer to be used for joints between infill masonry walls and r c frames

Abstract In the paper an idea to use a deformable polymer material for the joint between R.C. frames and masonry infills is presented. As an early step of testing the idea, experimental tests of the polymer in monotonic uniaxial tension at different load rates are performed and analyzed. The load rates range from very fast (8.3 mm/s) to very slow (0.00083 mm/s). The material exhibits a very strong strain rate effect and viscous behavior. In the second part of the paper a numerical model is developed and implemented into a finite element to simulate the results of the tests. The model is based on a new family of strain measures, called the Darjani-Naghdabadi strain measures and a classical viscosity formulation. Almost perfect model predictions up to collapse at 50-150% elongation are obtained by using calibration based on minimization of error

Unified cyclic stress–strain model for normal and high strength concrete confined with FRP

Fiber reinforced polymer (FRP) has become increasingly popular as a confining material for concrete, both in the strengthening of existing columns where FRP wraps with fibers oriented completely or predominantly in the hoop direction are typically used, and in new construction where filament-wound FRP tubes with fibers oriented at desired angles to the longitudinal axis are typically used. For both types of applications, the stress-strain behavior of FRP-confined concrete under cyclic axial compression needs to be properly understood and modeled for the accurate simulation of such columns under seismic loading. This paper presents an improved cyclic stress-strain model for FRP-confined concrete on the basis of a critical assessment of an earlier model proposed by Lam and Teng in 2009 by making use of a database containing new test results of both concrete-filled FRP tubes (CFFTs) and concrete cylinders confined with an FRP wrap. The assessment reveals several deficiencies of Lam and Teng\u27s model due to the limited test results available to them. The proposed model corrects these deficiencies and is shown to provide reasonably accurate predictions for both concrete in CFFTs and concrete confined with an FRP wrap and for both normal strength concrete (NSC) and high strength concrete (HSC)

Impact of minimal residual disease detection by next-generation flow cytometry in multiple myeloma patients with sustained complete remission after frontline therapy

Minimal residual disease (MRD) was monitored in 52 patients with sustained CR (≥2 years) after frontline therapy using next-generation flow (NGF) cytometry. 25% of patients initially MRD- reversed to MRD+. 56% of patients in sustained CR were MRD+; 45% at the level of 10−5; 17% at 10−6. All patients who relapsed during follow-up were MRD+ at the latest MRD assessment, including those with ultra-low tumor burden. MRD persistence was associated with specific phenotypic profiles: higher erythroblasts’ and tumor-associated monocytes/macrophages’ predominance in the bone marrow niche. NGF emerges as a suitable method for periodic, reproducible, highly-sensitive MRD-detection at the level of 10−6

Upgraded experimental database of uniformly FRP confined concrete columns for assessment of existing recommendations

Current studies concerning statistical elaboration and review of existing experimental results in databases, usually include only the characteristic maximum bearing stress and corresponding strain values as well as the failure values. In cases of uniform confinement failure values may be defined at 20% or 15% drop of maximum load or when the FRP jacket is fractured. Several recommendations include additional failure criteria related to lateral strain level or axial strain level in order to ensure the integrity of the columns or avoidance of shear failures among else. An experimental database based on the whole stress-strain response curves is presented, providing significant data necessary for the extensive assessment of the existing design models. The experimental database contains information on: a) the failure stress and strain values, b) on the stress and strain values at the level of 0.4% lateral strain as well as c) on the stress at the level of 1% axial strain. FRP confinement strength models recommended by existing guidelines are compared against experimental values

Peak strength and ultimate strain prediction for FRP confined square and circular concrete sections

It is widely accepted that axially loaded FRP confined concrete presents significant strength and ductility increase with reference to the unconfined case. Adequate FRP confinement provides bilinear - like and hardening stress-strain behavior to concrete up to failure. Therefore, to model the mechanical behavior of adequately confined concrete two quantities are necessary: peak strength and ultimate strain. Many studies have been published regarding confinement of circular section elements; fewer studies analyze the case of square and rectangular section. Numerous predictive expressions of peak strength and ultimate strain, suitable for circular section elements, are available. Only in recent years, complete equations have been proposed to cover both circular and square sections. The aim of this work is the assessment of the performances of significant predictive expressions published in literature. Four groups of predictive expressions have been considered; they differ by the type of the predictive quantity (peak strength or ultimate strain) and by their applicability (only circular sections or both circular and square sections). For this reason a wide database has been assembled; it collects results of more than 655 compressive tests, performed on square and circular specimens confined with FRP. This comparison has been diversified as a function of cross section shape and FRP type (CFRP, GFRP, AFRP)

Three-dimensional finite element model for FRP-confined circular concrete cylinders under axial compression

This paper presents a 3D FE model for FRP-confined circular concrete cylinders based on a plastic-damage constitutive model for concrete recently proposed by Yu et al. (2010b). This 3D model is capable of modeling deformation non-uniformity in the axial direction due to factors such as end restraints. Numerical results obtained using the FE model for FRP-confined cylinders with end restraints or with a vertical gap in the FRP jacket conform to expected trends although their quantitative accuracy awaits confirmation by laboratory tests. This FE model has the potential for extension to more general cases of FRP-confined concrete columns (e.g. rectangular concrete columns) and can provide a useful tool for the exploration of confinement mechanisms in the development of simple stress-strain models for design use